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Disinfection by-product formation and mitigation
strategies in point-of-use chlorination of turbid and
non-turbid waters in western Kenya
D. S. Lantagne, B. C. Blount, F. Cardinali and R. Quick
ABSTRACT
D. S. Lantagne (corresponding author)
R. Quick
Enteric Diseases Epidemiology Branch, M/S A-38,
Centers for Disease Control and Prevention,
1600 Clifton Road NE, Atlanta GA 30333,
USA
Tel.: 404 639 0231
Fax: 404 639 2205
E-mail: dlantagne@cdc.gov
B. C. Blount
F. Cardinali
Division of Laboratory Sciences,
National Center for Environmental Health,
U.S. Centers for Disease Control and Prevention,
Atlanta, GA 30341,
USA
Over 1.1 billion people in the world lack access to improved drinking water. Diarrheal and other
waterborne diseases cause an estimated 2.2 million deaths per year. The Safe Water System
(SWS) is a proven household water treatment intervention that reduces diarrheal disease
incidence in users in developing countries. Because the SWS recommends the addition of sodium
hypochlorite to unfiltered water sources, concerns have been raised about the potential long-
term health effects of disinfection by-products to SWS users. This study investigated the
production of trihalomethanes (THMs) in water treated with sodium hypochlorite from six sources
used for drinking water in western Kenya. The turbidity values of these sources ranged from
4.23 NTU to 305 NTU. THM concentrations were analysed at 1, 8, and 24 hours after addition of
sodium hypochlorite. No sample exceeded the World Health Organization (WHO) guideline values
for any of the four THMs: chloroform, bromodichloromethane, dibromochloromethane, or
bromoform. In addition, no sample exceeded the WHO additive total THM guideline value. These
results clearly show that point-of-use chlorination of a variety of realistic source waters used for
drinking did not lead to THM concentrations that pose a significant health risk to SWS users.
Key words
|
developing countries, disinfection by-products, drinking water, household water
treatment, point-of-use chlorination, Safe Water System
INTRODUCTION
Point-of-use water treatment and the Safe Water
System
An estimated 1.1 billionpeople lack access to improved water
supplies and2.4 billion people are withoutadequate sanitation
(WHO/UNICEF 2000). The health consequences of
inadequate water and sanitation services include an estimated
4 billion cases of diarrhea and 2.2 million deaths each year,
mostly among young children in developing countries
(WHO/UNICEF 2000). In addition, waterborne diarrheal
diseaseslead to decreased food intakeand nutrient absorption,
malnutrition, reduced resistance to infection (Baqui et al.
1993), and impaired physical growth and cognitive develop-
ment (Guerrant et al. 1999). Recently, point-of-use drinking
water treatment and safestorage optionshave been recognized
as approaches which can accelerate the health gains associ-
ated with improved water until the longer term goal of
universal access to piped, treated water can be attained
(Fewtrell & Colford 2004). Household water treatment and
storage practices can prevent disease, and thereby support
poverty alleviation and development goals.
Chlorination was first used for disinfection of public
water supplies in the early 1900s, and is one factor that
contributed to dramatic reductions in waterborne disease in
cities in the United States (Cutler and Miller 2005).
Although small trials of point-of-use chlorination had
been implemented in the past (Mintz et al. 1995), larger
scale trials began in the 1990s, as part of the Pan American
doi: 10.2166/wh.2007.013
67 QUS Government 2008 Journal of Water and Health
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Health Organization (PAHO) and the U.S. Centers for
Disease Control and Prevention (CDC) response to
epidemic cholera in Latin America (Tauxe 1995). The Safe
Water System (SWS) strategy devised by CDC and PAHO
includes three elements: water treatment with dilute sodium
hypochlorite at the point-of-use, storage of water in a safe
container, and behavior change communication to improve
hygiene and water and food handling practices. The sodium
hypochlorite solution is packaged in a bottle with directions
instructing users to add one full bottle cap of the solution to
clear water (or 2 caps to turbid water) in a standard sized
storage container, agitate, and wait 30 minutes before
drinking. In five randomized controlled trials, the SWS
has resulted in reductions in diarrheal disease incidence
ranging from 26–84% (Semenza 1998;Quick 1999;Quick
2002;Luby 2004;Crump et al. 2005).
The standard Safe Water System sodium hypochlorite
dosage provides a maximum CT factor of 56.25 mg-min/L.
A CT factor of 56.25 is sufficient to inactivate most bacteria,
viruses, and some protozoa (such as giardia) which cause
waterborne diseases (CDC 2006). It will not inactivate
Cryptosporidum and populations at risk for Cryptospo-
ridum infection should consider a filtration step prior to
chlorination to remove the oocysts.
This well-documented reduction of diarrheal disease
incidence in SWS users has encouraged non-governmental
organizations (NGOs) and governments to broadly dis-
seminate the program. National, regional, and local SWS
projects have been implemented with NGO and govern-
ment partners in over 20 countries since 1998. As access to
the SWS has expanded in developing countries, where
many water sources contain suspended organic material,
some health officials and implementing organizations have
expressed concern about the formation of disinfection
by-products in treated water and the attendant risk to users.
Trihalomethanes
In 1974, Rook discovered that hypochlorous acid and
hypobromous acid react with naturally occurring organic
material to create four compounds with potential human
health effects: chloroform (CHCl
3
), bromoform (CHBr
3
),
bromodichloromethane (CHCl
2
Br), and dibromochloro-
methane (CHClBr
2
)(Rook 1974). These four compounds
are collectively termed trihalomethanes (THMs). Initially,
research focused on the long-term health effects of chloro-
form and the other trihalomethanes, however, further
research has shown that chlorination of drinking water
leads to the formation of numerous compounds that may or
may not have mutagenic activity. Richardson et al. (2002)
identified greater than 600 water disinfection byproducts in
chlorinated tap water, including haloacetic acids (HAAs).
THMs, and to a lesser extent HAAs, are currently used by
regulatory agencies as indicator chemicals for all potentially
harmful compounds formed by the addition of chlorine to
water.
The World Health Organization (WHO) has estab-
lished guideline values for trihalomethane exposure, based
on epidemiological and laboratory studies. The guideline
values are based on an allowable risk of one extra cancer
attributable to THM exposure in 100,000 people who ingest
two litres of chlorinated water per day with trihalomethane
concentrations at the guideline value for a lifetime period of
70 years.
Chloroform has been classified as possibly carcinogenic
to humans, based on sufficient evidence for carcinogenicity
in experimental animals but inadequate evidence in humans
(IARC 1999). The WHO guideline value for chloroform is
300 mg/L (300 parts per billion (ppb)) (WHO 2005).
Bromodichloromethane (BDCM) has been classified as
probably carcinogenic to humans, with sufficient evidence
in animals and inadequate evidence in humans (IARC 1991).
The WHO guideline value for BDCM is 60 mg/L (WHO
2004). Both dibromochloromethane (DBCM) and bromo-
form have been classified as not classifiable in humans for
carcinogenicity (IARC 1991), and the WHO guideline values
for both are 100 mg/L (WHO 2004)
1
.
WHO also proposes the use of an additive toxicity
guideline value, using the fractionation equation that the
sum of the four THMs’ actual concentration (C) divided
by their guideline value (GV) should not be greater than
1
Note that the publication Trihalomethanes in Drinking-Water (WHO 2005) supersedes
the 3rd Edition of the Guidelines for drinking-water quality (WHO 2004) with an updated
chloroform guideline value. The chlorine guideline value has been increased from
200 mg/L in 1993 to 300 mg/L in 2006 due to an increase in the proportion of chloroform
exposure attributed to drinking water (with low chloroform concentrations) and a
decrease in the proportion of chloroform exposure from other mechanisms (with higher
chloroform concentrations). This updated guideline value will be formalized in an
addendum to the Guidelines for drinking-water quality anticipated in early 2007 (Bartram
personal communication 2006).
68 D.S. Lantagne et al.
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one (WHO 2004).
CChloroform
GVChloroform
þCBDCM
GVBDCM
þCDBCM
GVDBCM
þCBromoform
GVBromoform
#1ð1Þ
In addition, the WHO Guidelines specifically state that:
‘Where local circumstances require that a choice must be
made between meeting either microbiological guidelines or
guidelines for disinfectants or disinfectant by-products, the
microbiological quality must always take precedence, and
where necessary, a chemical guideline value can be adopted
corresponding to a higher level of risk. Efficient disinfection
must never be compromised’ (WHO 1993).
In contrast to the health-based WHO THM guidelines, the
USEPA and other developed country regulatory agencies
regulate the reduction of trihalomethane concentrations in
drinking water through technology improvements to ‘provide
an incremental step towards mitigating potential risks’ and
‘potential health concerns’ (USEPA 2006). The USEPA
maximum contaminant level (MCL) for total trihalomethanes
(there are no individual analyte thihalomethane USEPA
MCLs) is currently 80 mg/L. In response to these regulations,
the majority of the trihalomethane literature has analyzed
trihalomethane formation potential of source waters and
mitigation strategies such as the use of alternate disinfectants
in centralized water treatment plants in developed countries.
No known research to date has examined the formation
of trihalomethanes consequent to household water treatment
with sodium hypochlorite, which is the most practical form of
treatment in many parts of the world lacking piped water
supplies. In September 2003, we conducted research on
trihalomethane formation resulting from the chlorination of
stored water from a variety of sources with varying turbidity
levels, and the effectiveness of several potential mitigation
strategies, in rural Western Kenya, where CDC and the
NGOs CARE International and Population Services Inter-
national operate an SWS program which began in 1999.
METHODS
Setting
This study was conducted in September 2003 in areas
surrounding Homa Bay, which is south of Kisumu on Lake
Victoria in rural western Kenya. Previous studies have
found that SWS users in this region access a wide variety of
drinking water sources, with low to extremely high turbidity
levels (Ogutu et al. 2001;Crump et al. 2004). In one study
that examined 30 samples from a variety of surface and
borehole water sources in Western Kenya, the mean
turbidity was 331.9 Nephalometric Turbidity Units
(NTUs), with a range of 0.3 to 1724 NTUs (Crump et al.
2004). The addition of sodium hypochlorite in the house-
hold to this water led to a 26% reduction in diarrheal
disease risk among users as compared to controls who
implemented safe storage practices only (Crump et al. 2005).
Study design
We analyzed THM concentrations after chlorination in six
different water sources which were used for drinking by
local communities: lake, river, earth pond, protected well,
open well, and rainwater catchment system (Figure 1).
To assess whether use of different types of water storage
containers led to different THM exposure risk, water
treatment procedures were conducted in water stored in
both 20-litre HDPE plastic jerry cans and locally purchased
ceramic pots. The jerry cans were cleaned, recycled
vegetable oil containers which are widely used as water
storage containers throughout Africa. The ceramic water
storage pots are the preferred storage container in many
parts of Africa because they are locally available from
potters, inexpensive, and the stored water is cooled by
transpiration through the ceramic pores.
For each of the six water sources, THM concentrations
were measured after three different treatment procedures
were used in plastic jerry cans and in ceramic pots (Table 1):
1) after the addition of sodium hypochlorite solution; 2) after
filtration of sample water through a commonly available local
cloth before adding sodium hypochlorite; and 3) after settling
of the water for 24 hours and decanting supernatant water
before adding sodium hypochlorite. In addition, samples
in plastic jerry cans were treated with the alternate point-of-
use water treatment product PuR
Y
(Procter & Gamble
Company, Cincinnati, OH, USA), and samples in ceramic
pots were pre-treated with the natural flocculant moringa
seeds. PuR
Y
and moringa seeds were not tested in both plastic
and ceramic containers due to sample number limitations,
and thus it was decided to test the commercial PuR
Y
product
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in plastic jerry cans and the local moringa seeds, normally
used in rural areas, in the locally-made ceramic pots.
A 1% sodium hypochlorite solution, marketed under the
brand name WaterGuard by Popula tion Services International
(PSI) (Figure 2), was used in the study. Two 500ml bottles of
WaterGuard were purchased locally, and each was tested to
ensure correct concentration with a Hach (Loveland, CO)
Method 8209 portable iodimetric digital titration kit for high-
range total chlorine. The sodium hypochlor ite concentration of
the two bottles was 0.96% and 1.02%, respectively, which
reflects non-concerning variation of concentration in the
production process. An 8 ml (1 capful) volume from one of
the two containers was added to water in plastic containers
from all sources except the river water, to which 16 ml (two
capfuls) was added. For the ceramic pots, 8 ml (1 capful) of
1.02% WaterGuard sodium hypochlorite solution was added
to earth pond water; 16 ml (two capfuls) of 0.96% or 1.02%
sodium hypochlorite solution was added to rainwater, open
well water, protected well water, and lake water; and 24ml
(three capfuls) of 1.02% solution was added to the river water.
This dosing regime, and the difference from the dosing in the
plastic containers, was developed by Ogutu et al. (2001) in
response to concern that organic material in the ceramic pots
would exert additional chlorine demand than in plastic
Figure 1
|
Water sources used in study (Clockwise from top left: rainwater catchment, lake, protected well, earth pond, river). Note the open well source was not photographed.
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containers. This dosage is double the amount of chlorine
recommended currently in Safe Water System programs,
including in Kenya. Based on additional chlorine demand
testing in both plastic and ceramic containers, the new
recommended dose for Kenya is 1.875 mg/L of chlorine in
clear sources, and 3.75 mg/L in turbid sources in both plastic
and ceramic containers. The utilization of this older dosing
regime provides a worst-case scenario of trihalomethane
formation potential for Safe Water System programs.
A sachet of the Procter & Gamble point-of-use treatment
product,PuR
Y
, includesa proprietary mixtureof the flocculant
ferrous sulphate and the disinfectant calcium hypochlorite.
PuR
Y
sachets are now marketed in Kenya by PSI, but for this
study sachets were obtained in the United States. A sachet was
added to 10 litres of water, which was stirred for five minutes,
allowed to settle, and then poured through a locally-available
cloth to remove the floc.
The natural flocculant Moringa oleifera pods were
obtained locally. Pods were opened to remove the seeds,
which were peeled and crushed into a powder using a
mortar and pestle. Two grams of the powder was measured
on a digital scale and were added to 20 litres of water
(Madsen et al. 1987), stirred for 5 minutes, and allowed to
settle for 24 hours before supernatant water was decanted
off and treated with sodium hypochlorite. The coagulation
properties of moringa are attributed to polypeptides acting
as cationic polymers (Madsen et al. 1987).
Water collection
Water from each of the six sources was collected in eight
clean 20 litre plastic jerry cans and transported to the lab
the day before analysis occurred.
Water testing procedures
On each day of analysis, each source water sample was
tested for chemical and bacteriological water quality
parameters before treatment began to characterize the
source water, ensure samples with well differentiated
water quality characteristics were collected, and provide
appropriate data for regression analysis.
Each water sample was analyzed for turbidity, pH,
ammonia, conductivity, temperature, free and total chlo-
rine, and total coliform and Esherichia coli colony counts.
In addition, a water sample was collected for later analysis
for total organic carbon (TOC) in a glass container, acidified
to a pH below 2.0, and stored on ice below 68C for later
analysis in the United States. Total organic carbon samples
were delivered to Analytical Services, Incorporated
(Norcross, GA, USA) within two weeks of collection.
EPA Method 9060 was used to analyze the samples, and
all laboratory quality control guidelines were met.
Turbidity was measured after agitation of the sample
water with a Lamotte 2020 turbidimeter (Cherstertown, MD,
Table 1
|
Water storage, clarification, and treatment procedures completed for each of six water sources
Container type Water clarification procedure Disinfection procedure
1 Plastic None Sodium hypochlorite
2 Plastic Filtered through cloth Sodium hypochlorite
3 Plastic Settled for 24 hours and decanted Sodium hypochlorite
4 Plastic PuR
Y
(ferrous sulphate) PuR
Y
(Calcium hypochlorite)
5 Ceramic None Sodium hypochlorite
6 Ceramic Filtered through cloth Sodium hypochlorite
7 Ceramic Settled for 24 hours and decanted Sodium hypochlorite
8 Ceramic Moringa addition for 24 hours and decanted Sodium hypochlorite
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USA) calibrated weekly with non-expired stock calibration
solutions. pH and conductivity were measured with a Hanna
multimeter (Bedfordshire, UK) calibrated weekly with non-
expired stock calibration solutions. Temperature was
measured with an Envirosafe
w
non-mercury thermometer
(Ben Meadows Company, Jainsville, WI, USA). Ammonia
was measured with an Aquarium Pharmaceuticals, Inc.
Ammonia NH
3
/NH
4
test kit (Oxfordshire, UK).
Free and total chlorine were measured immediately
after sample collection using a Lamotte 1200 single
wavelength chlorine colorimeter and DPD-1 and DPD-3
tablets (Chestertown, MD, USA). The meter was calibrated
daily using non-expired stock calibration solutions at 0, 0.1,
1.0, and 2.65 mg/L free chlorine.
Total coliform and E. coli were measured using a
portable Millipore (Billerica, MA, USA) filtration stand and
mColiBlue24 media. Samples were diluted appropriately
with sterile buffered water, filtered aseptically through a
45-micron filter, placed in a petri-dish with a media soaked
pad, and incubated for 24 hours at 358C following Standard
Methods (1998). Negative controls were included within
each daily run.
For each of the six water sources, at 1 hour, 8 hours, and
24 hours after each treatment procedure was completed in
the plastic jerry cans and the ceramic containers, three
water quality testing procedures were completed: 1) Free
and total chlorine were measured using the procedures
detailed above; 2) Total coliform and E. coli samples were
collected and analyzed on site using the procedures detailed
above; and 3) An THM sample was collected and stored on
ice for later analysis in the United States.
Trihalomethane sampling
Samples for THM testing were collected by using a pre-
cleaned 40 ml VOA vial to transfer liquid into a pre-cleaned
12 ml glass vial containing 125 ml of a bufferquench solution
(Cardinali et al. 2004). The 12 ml vial was slightly overfilled
to create an inverted meniscus and avoid air bubbles. The
sample vials were then sealed with Teflon-lined silicone
septa and stored in a cool (4 –88C temperature range) and
dark location. Samples were stored no longer than two
weeks before delivery to the Division of Laboratory
Sciences at the National Center for Environmental Health,
CDC, for analysis of trihalomethanes (THMs).
Water samples were analyzed for THMs (chloro-
form, bromodichloromethane, dibromochloromethane,
and bromoform) using stable isotope dilution headspace
SPME GC–MS (Cardinali et al. 2004). Briefly, water vials
were removed from refrigerated storage and allowed to
equilibrate to room temperature before analysis. Immedi-
ately after removal of the vial cap, water (5.0 ml) was
removed using a pre-cleaned gas-tight syringe and trans-
ferred into an SPME headspace vial. Stable isotope labeled
analog solution was added to the sample and the SPME vial
immediately crimp-sealed using Teflon-lined septum.
We analyzed samples using SPME/GC–MS on a
ThermoFinnigan TraceMS (ThermoFinnigan, Austin, TX,
USA) attached to a Trace 2000 gas chromatograph
equipped with a split/splitless injector and operated in the
Figure 2
|
The PSI Kenya WaterGuard product.
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splitless mode. Because of the volatility of THMs, a
cryo-trap (model 961, Scientific Instrument Services, Ring-
oes, NJ, USA) was used to cryofocus the analytes at the
head of the GC column. VOCs were chromatographically
separated on a VRX capillary column (20 m £0.18 mm
i.d. £1.0 mm film, Restek, Bellefonte, PA, USA) during a
thermal gradient from 208C to 2008C. Automated sampling
was done using a CombiPAL autosampler (CTC Analytics
AG, Zwingen, Switzerland) equipped with a 75-mm Car-
boxen/PDMS SPME fiber assembly (Supelco, Bellefonte,
PA, USA) and heated/agitated headspace extraction (8 min,
500 rpm, 508C). The fiber was promptly desorbed by
insertion into the hot GC inlet (2008C). The mass
spectrometer was equipped with an electron impact source
and run in the selected ion monitoring (SIM) mode at unit
mass resolution. Xcalibur Quan software (ThermoFinnigan,
Austin, Texas, USA) was used for peak integration,
calibration, and quantification. We performed peak inte-
grations with ICIS integrator and confirmed by visual
inspection. We calculated relative response factors on the
basis of the relative peak areas of analyte quantitation ion
and labeled analog ion. Quality control consisted of daily
analysis of blind quality control material and pure water
blanks. Trihalomethanes were quantified by comparing the
ratios of analyte peak areas with labeled analog areas for
both unknowns and freshly prepared calibrators.
Data analysis
All data were entered into Microsoft Excel, and the
Analysis ToolPak regression tools were utilized to analyze
the data.
RESULTS
Source water quality
Results of the water quality testing are presented in Table 2.
A wide range of turbidity (4.2 – 305 NTU) and TOC
(0–7 mg/L) values were found in water from the six
sources. Turbidity and TOC values, however, were not
related (R
2
¼0.03). The lowest and highest turbidity values
were seen in rainwater catchment and river water, respect-
ively. The lowest and highest TOC values were seen in the
open well water and earth pond water, respectively.
The WHO has established a maximum recommended
pH value for chlorination of water of 8.0, as chlorine is less
effective at inactivating microorganisms at higher pH values
(WHO 2004). The only pH value that exceeded this
recommendation in source waters in this study was
obtained from earth pond water. Conductivities were well
differentiated (10 –770 mmhos/cm). Conductivity is a
measure of the ionic material dissolved in the water,
Table 2
|
Source water physical and chemical characteristics and microbiological water quality
Source 1: Rainwater
catchment Source 2: Lake Source 3: Protected well Source 4: Earth pond Source 5: River Source 6: Open well
Turbidity (NTU) 4.2 28.2 40.4 59.6 305 8.4
TOC (mg/L) 2 4 1 7 3 ,1
pH 6.9 8.0 6.7 8.6 7.2 7.2
Conductivity (mmhos/cm) 10 160 260 200 70 770
Temperature (8C) 19.5 23.5 22 23.5 23.0 23.5
Ammonia (mg/L) 0 – 0.25 0 –0.25 0–0.25 0–0.25 0–0.25 0–0.25
Total coliform (col/100 ml) 3,550 10,600 6,700 5,200 57,000 .4,000
E. coli (col/100 ml) 350 285 220 700 2,700 50
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including chloride. Chlorine and bromide are often closely
related, and thus conductivity is potentially related to
bromide concentration. The lowest and highest conduc-
tivity values were seen in rainwater catchment and open
well water, respectively.
Source water temperatures were normal for the Western
Kenya region, ranging from 19.5– 23.58C. Ammonia values in
all samples were at a similarly low, undifferentiated level. No
source had detectable free or total chlorine before treatment.
All sources, whether protected or not, were contaminated
with total coliform (range 3,550– 57,000col/100 ml) and
E. coli (range of 50 –2,700 col/100 ml) at concentrations
that far exceed the WHO drinking water guideline
values of ,1 col/100ml for both total coliform and E. coli
(WHO 2004).
Water quality characterization of the six source waters
demonstrated that they were well differentiated in terms of
TOC, turbidity, and conductivity, and therefore provided
appropriate data for regression analysis.
Quality control
Duplicate sampling was conducted for each water quality
parameter tested. All data met high quality control
standards (Table 3). The relative percent difference (RPD)
of duplicated samples was 5.3% for turbidity, 1.76% for pH,
0.0% for conductivity, 0.0% for temperature, and 0.0% for
ammonia. On average, the RPD of duplicated free chlorine
samples was 12.6%, and of duplicated total chlorine
samples was 5.7%.
For quality control of microbiologic testing, an R
2
value
was calculated in place of RPD to account for readings of
0 col/100 ml. Results for original and duplicate water
samples were highly correlated for E. coli (R
2
¼0.997)
and total coliform (R
2
¼0.943).
All THM quality control materials were evaluated using
Westgard rules (Westgard 1981). Of 143 total samples
analyzed for THM concentration, 47 (32.9%) were dupli-
cated. Each of the duplicate samples was analyzed for all
Table 3
|
Quality control for water quality parameters
Total samples collected Number and percent of duplicated samples Relative percent difference R
2
Free chlorine 144 28 (19.4%) 12.6%
Total chlorine 144 22 (15.3%) 5.7%
E. coli 131 41 (31.3%) – 0.997
Total Coliform 131 33 (25.2%) – 0.943
Turbidity 57 6 (10.5%) 5.3%
pH 6 3 (50%) 1.76%
Conductivity 6 3 (50%) 0%
Temperature 6 1 (16.7%) 0%
Ammonia 6 1 (16.7%) 0%
Trihalomethanes 572 188 (32.9%) 3.59%
Chloroform 143 47 (32.9%) 2.76%
Bromodichloromethane 143 47 (32.9%) 2.42%
Dibromochloromethane 143 47 (32.9%) 1.32%
Bromoform 143 47 (32.9%) 7.85%
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four THMs, for a total of 188 duplicate trihalomethane
results, 47 for each analyte. The average RPD of the 188
samples was 3.89%, with only 5 (2.7%) of the 188 individual
analyte duplicate samples exceeding a 10% RPD. The
individual RPDs for chloroform, bromodichloromethane,
dibromochloromethane, and bromoform were 2.76%,
2.42%, 1.32%, 7.85%, respectively (Table 3).
Overall THM data
Results from all 143 samples analyzed for the four individual
THMs are presented in Table 4. One sample broke in transit.
No sample exceeded the WHO guideline values for any of the
four individual THMs.
The WHO additive ratio guideline values ranged from
0.004 to 0.997, with a mean of 0.285 and a standard
deviation of 0.199. Thus, all samples also met the additive
guideline value: the sum of the four THMs’ actual values
divided by their guideline value should not be greater
than one.
The average relative percentage for all treatment types of
the individual THM analytes and the average concentration
of individual THM analytes by source is presented in
Table 5. There was no significant difference seen in
individual analyte percentage between the plastic and
ceramic containers. Chloroform was the dominant analyte
in the rainwater, lake water, protected well water, earth
pond water, and river water (74.9–95.2% of the total
trihalomethanes (TTHM)), with correspondingly low per-
centages of the DBCM and bromoform analytes. In the
open well water source, there was substantially lower
chloroform (47.9%), and correspondingly higher BDCM
and DBCM percentages.
The percent chloroform was related to the conductivity
of the source water as shown in Equation 2:
Percent Chloroform¼20:0565£Conductivityðmmhos=cmÞ
þ91:1
R2¼0:9414;p2value 0:0013
ð2Þ
Conductivity is inversely related to the percent chloro-
form, accounting for 94% of the variance in the percent
chloroformin the six samples, and can thereforebe considered
a good indicator of bromide concentration in these waters.
Sources with higher bromide concentrations (with corre-
sponding increases in the conductivity due to the presence of
the dissolved ionic chloride and thus bromide), such as open
well water, will have a lower chloroform percentage, and
higher percentage of the brominated trihalomethanes, in the
treated water. Presence of bromine impacts the additive
guideline value results as well, as the individual guideline
value for chloroform is higher than the individual guideline
values for the brominated trihalomethanes.
No significant variation was seen in the individual THM
percentages between plastic and ceramic containers. Because
of this lack of variation in individual THM percentages, in the
followinganalysis by treatment methodology, allresults will be
presented as TTHMs, which is the summation of the four
individual trihalomethane analytes. The analysis will focus on
samples collected at 24 hours after chlorine addition, as this is
the highest TTHM value seen in the samples. Supplementary
analysis by individual analyte is available from the authors.
Sixteen of the 48 samples (33%) taken at 24 hours after
chlorine addition exceeded the USEPA MCL for TTHM. Two
of the twelve total chlorination only samples exceeded the
Table 4
|
Individual analyte trihalomethane results, all samples
Average (ppb) Minimum (ppb) Maximum (ppb) Standard deviation (ppb) WHO guideline value (ppb)
Chloroform 43.4 0.6 160 36.4 300
Bromodichloromethane 7.2 0.1 33.0 5.6 60
Dibromochloromethane 2.0 0.0 8.1 1.9 100
Bromoform 0.1 0.0 1.1 0.2 100
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USEPA MCL for TTHM, from the river water in plastic and
ceramic containers.
Chlorination only in plastic containers
Free chlorine residual was maintained in water from all
sources for 24 hours (range 0.07 –3.64 mg/L). Water
samples from all sources had no detectable E. coli colonies
at 1 and 8 hours after treatment, however, at 24 hours in the
lake water and the earth pond water, there was slight
regrowth of E. coli (12 and 32 col/100 ml, respectively).
The chlorine residual levels in these sources at 24 hours
were low, at 0.10 and 0.33 mg/L, respectively.
No sample using treatment with sodium hypochlorite
solution only in plastic containers exceeded any of the
WHO guideline values for the four individual THMs.
TTHM results over time for these samples are presented
in Figure 3. TTHM at 24 hours was strongly correlated with
turbidity, according to the equation:
TTHM ðmg=LÞ¼0:3692 £Turbidity ðNTUÞþ40:2
R2¼0:8907;p2value 0:0084
ð3Þ
Turbidity accounted for 89% of the variance in the
TTHM concentration at 24 hours. In the regression analysis,
there were no statistically significant correlations between
the other source water quality parameters, including TOC,
and TTHM concentrations at 24 hours.
The WHO additive ratio guideline valueresults at 24 hours
ranged from 0.182 to 0.674, well below the WHO guideline
value of lessthan one, with the protected wellwater lowest and
the river water highest. The open well water had relatively
higher additive guideline values due to the higher proportion
of bromodichloromethane, which has a lower guideline value
than the other trihalomethanes.
Potential mitigation strategies: Filtration, settling &
decanting, and PuRYin plastic containers
Neither filtration nor settling & decanting showed any
statistically significant reduction of THM levels at 1, 8, or
24 hours after chlorine addition, indicating that the THM
precursors are smaller particles than are removed by filtration
or settling & decanting. In fact, there was little difference in
the resultant TTHM values when the chlorination only
Table 5
|
Average individual THM percentage and concentration by source
Source Chloroform Bromodichloromethane Dibromochloromethane Bromoform
1: Rainwater 95.2% 4.5% 0.3% 0%
42.88 mg/L 2.13 mg/L 0.17 mg/L ,0.1 mg/L
2: Lake water 78.4% 18.2% 3.4% 0%
45.63 mg/L 9.26 mg/L 1.70 mg/L ,0.1 mg/L
3: Protected well water 75.2% 17.4% 7.0% 0.4%
16.71 mg/L 3.99 mg/L 1.57 mg/L 0.09 mg/L
4: Earth pond water 74.9% 19.6% 5.2% 0.3%
56.46 mg/L 14.10mg/L 3.50 mg/L 0.18 mg/L
5: River water 90.1% 9.1% 0.8% 0.0%
84.02 mg/L 7.4 mg/L 0.53 mg/L ,0.1 mg/L
6: Open well water 49.7% 26.6% 20.8% 2.9%
13.50 mg/L 6.08 mg/L 4.40 mg/L 0.57 mg/L
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results are compared with these two potential mitigation
strategies (Figure 4). The rainwater results presented in
Figure 4 are similar to the other five sources tested. The use of
these two pretreatments did not consistently reduce turbidity
and maintain higher chlorine residuals at 24 hours after
chlorine addition as compared to the chlorination only
samples, and this accounts for the lack of statistically
significant TTHM reduction.
In contrast, PuR
Y
was a very effective mitigation strategy.
After the use of PuR
Y
, turbidity in the samples dropped from a
range of 4.23–305 NTU to a range of 0.93–2.1 NTU. On
average, in the six different source samples when compared
with the chlorine only samples, TTHM levels were 26.1%
lower at 1 hour after treatment, 65.0% lower at 8 hours, and
73.1% lower at 24 hours in PuR
Y
treated samples. All
individual and TTHM values were very low (Figure 5), and
the WHO additive ratio guideline value results at 24 hours
ranged from 0.015–0.183. No significant relationship was
seen between TTHM and any of the water quality variables.
Low levels of free chlorine residual were maintained using
PuR
Y
in all six water sources after 24 hours, ranging from
0.08 –0.32 mg/L, and there was no regrowth of E. coli.
Chlorination only in ceramic containers
Free chlorine residual was maintained in all stored water
samples from all sources for 24 hours after chlorine addition
(range 0.28– 3.5 mg/L). All E. coli were removed in the six
sources and all sources remained E. coli free at 24 hours.
No chlorination only samples in ceramic containers
exceeded any of the WHO guideline values for the four
individual THMs. TTHM results over time for these samples
are presented in Figure 6. TTHM at 24 hours was correlated
with turbidity using the following equation:
TTHM ðmg=LÞ¼ 0:2925 £Turbidity ðNTUÞþ48:7
R2¼0:6648;p2value 0:0606
ð4Þ
Turbidity of the source water accounted for 66% of the
variability in the TTHM concentrations at 24 hours. In the
regression analysis, there were no statistically significant
Figure 3
|
TTHM versus time in plastic containers, chlorination only.
Figure 4
|
TTHM versus time in rainwater using plastic containers and four treatments.
77 D.S. Lantagne et al.
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correlations between the other source water quality para-
meters, including TOC, and TTHM concentration at 24
hours. These findings were similar to those obtained in
water stored in plastic containers. The reason for the low
TTHM value in the 24–hour earth pond water sample is
unknown (Figure 6). This value is considered an outlier and
was excluded from the regression analysis due to this
unexplained TTHM drop over time, which might be
attributable to sampling error.
The WHO additive ratio guideline value results at 24
hours were 0.142 to 0.607 (as compared with the chlorination
only values in the plastic containers of 0.182 to 0.674), with
the protected well water lowest and the river water highest
(the same as in the chlorination only samples in plastic
containers). These results were strikingly similar to the
chlorination only values in the plastic containers (Table 6).
Potential mitigation strategies: Filtration, settling &
decanting, and moringa in ceramic containers
Both filtration and settling and decanting showed no
statistically significant reduction of TTHM levels at 1, 8, or
24 hours after chlorine addition. In fact, in ceramic pots, as in
the plastic containers, there was little difference in the
Figure 5
|
TTHM versus Time in Plastic Containers using PuR.
Figure 6
|
TTHM versus time in ceramic containers, chlorination alone.
78 D.S. Lantagne et al.
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resultant TTHM values between samples treated with chlori-
nation only and samples pre-treated with the two potential
mitigation strategies.
Moringa was also an ineffective THM formation
mitigation strategy. The 2-gram dose of moringa reduced
turbidity in medium turbidity source waters (lake, protected
well, and earth pond) (Table 7), but had less effect in river
water, and was ineffective in low turbidity rain water.
The use of moringa seeds as a flocculant resulted in little or
no reduction in TTHM concentration in treated water as
compared with the chlorination only samples. In fact, there
was a slight increase in TTHM concentration in five of the six
source samples at 24 hours as compared to the chlorination
only in ceramic container samples. The WHO additive ratio
guideline value results at 24 hours were 0.200 to 0.997, as
compared to the chlorination only values in the ceramic
containers of 0.142 to 0.607. The protected well water had the
lowest additive guideline value. The earth pond water had the
highest additive guideline value seen in the study, at 0.997.
DISCUSSION
No point-of-use treatment method, alone or in combination
with any pre-treatment method, yielded any samples that
exceeded WHO guideline values for any of the four
individual THMs or the additive TTHM ratio guideline
value irrespective of the water source or storage container.
This is not a surprising result, although the relatively low
percentage of samples that exceeded the USEPA MCL (33%
of samples at 24 hours after chlorine addition) is of note. In
contrast to public utilities in the United States and Europe,
which devote considerable expense to reducing trihalo-
methane concentrations in their treated water through
technology improvements as part of balancing the risk of
waterborne disease and reducing disinfection by-products
to “mitigate potential risks” (USEPA 2006), WHO simply
considers health effects and health risk to potential users
from exposure to a certain compound when developing
guideline values (WHO 2005). WHO has defined the
acceptable risk from the individual THMs as one extra
cancer in every 100,000 people who drink two litres of
chlorinated water for 70 years. WHO guidelines, which are
considered separately from the goal of providing highly
treated water through infrastructure, are applicable to the
Safe Water System, and other health-based point-of-use
water treatment interventions.
A significant difference in THM concentrations in water
stored in ceramic and plastic storage containers was not seen.
We added ceramic pots to the study to test whether the ceramic
would either absorb THMs, or add THM precursors to stored
water. The data clearly showed neither significant gains nor
losses of TTHMs in the ceramic container, suggesting that
TTHMs were not absorbed into the ceramic, and that organic
material with TTHM formation potential did not leach from the
ceramic containers into the stored water. It is likely that organic
material that would lead to THM formation potential was
burned off in the firing process of the ceramic.
The majority of TTHMs were formed within 8 hours
after chlorine addition, indicating that as chlorine residual
decays during storage, there is less TTHM production.
Pretreatment of water by filtration through a cloth or
settling for 24 hours and decanting supernatant water before
chlorination did not appear to be effective THM mitigation
strategies. Neither procedure reduced TTHM concentrations
in chlorinated water as compared to chlorination only. These
are not unexpected results, as THM precursor compounds
have been identified as primarily organic carbon particles
smaller than 0.45 microns in size (Chow et al. 2005). It is
unlikely that such gross filtration mechanisms as tested in this
study would remove such small particles. It was, however,
important to test these potential mitigation strategies, as they
are practical and inexpensive strategies available to and used
by the populations who are targeted by point-of-use water
treatment intervention programs like the Safe Water System.
Table 6
|
Comparison of plastic and ceramic results, chlorination only treatment
TTHM (ppb) in chlorination only treatment
at 24 hours after chlorine addition
Source Plastic containers Ceramic containers
1: Rainwater 47.4 78.2
2: Lake water 62.9 78.6
3: Protected well water 27.9 24.9
4: Earth pond water 75.1 47.3
5: River water 152.8 121.7
6: Open well water 39.8 34.1
79 D.S. Lantagne et al.
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There were inconclusive results as to whether the use of
these two pretreatment mechanisms increases the chlorine
residual present in stored water at 24 hours after chlorination
because of reduction in chlorine demand. It is recommended
that the impact of these pretreatment mechanisms on free
chlorine residual over time, as compared to chlorination only,
be further investigated to fully characterize their potential
effectiveness in maintaining free chlorine residual.
The use of PuR
Y
led to significantly lower TTHM
concentrations at 24 hours after treatment than the use of
chlorination only and was thus an effective TTHM mitigation
strategy. This finding was expected because PuR
Y
has been
proven to reduce turbidity (Crump et al. 2004). PuR
Y
is
marketed by PSI for sale in Kenya at a product cost-recovery
price of 7 Kenya Shillings (9.7 US cents) to treat 10 litres of
water (0.97 cents per litre). In contrast, the Safe Water System
product, WaterGuard (Figure 2), is marketed by the NGO
Population Services International (PSI) in Kenya at a product
cost-recovery price of 20 Kenya Shillings (27.8 US cents) to
treat 1,000 litres of water (0.0278 cents per litre). As both are
available to the Kenyan population, variables such as dis-
posable income and user preference will impact each family’s
choice of which household water treatment product to utilize.
Our findings suggest that the use of ground moringa seeds
increases TTHM concentrations as compared to chlorination
alone, particularly at 24 hours after the addition of sodium
hypochlorite solution. It is postulated that the addition of the
moringaresultedinanincreaseofTHMprecursorsinthewater,
which led to a corresponding higher THM formation potential
than would be expected in water chlorinated without moringa
pre-treatment. In addition, the dose of moringa necessary to
remove turbidity varied depending on the turbidity of the source
water. It is recommended that organizations promoting
moringa seed use for flocculation followed by chlorination for
disinfection consider the potentialimpactsofthiscombineduse
on TTHM concentrations. Further research should be con-
ducted to determine more appropriate use of moringa in waters
of different turbidity levels.
In this study, conductivity wasidentifiedasasurrogatefor
bromide concentration to predict THM speciation (R
2
¼0.94),
and turbidity was significantly related to TTHM concentration
at 24 hours after chlorine addition in both plastic (R
2
¼0.89)
and ceramic containers (R
2
¼0.66). The relationship between
conductivity and bromide is clear, as increases in the dissolved
ionic chloride concentration, which is related to bromide, will
lead to corresponding increases in the conductivity. Other
minerals and sodium chloride can also cause increases in
conductivity, so this result cannot be generalized. Turbidity has
traditionally been used in drinking water treatment as a
surrogate parameter for particle concentrations. While UV
254
absorbance has been identified as a surrogate indicator of THM
formation potential (Chow et al. 2005), it is more difficult to
measure in areas without access to a spectrophotometer
(Standard Methods 1998). It is recommended that, in situations
in which access to laboratory facilities is limited, further
research should consider using water quality parameters of
conductivity and turbidity as indicators for bromide concen-
tration and THM formation potential, respectively, because
they can be accurately measured in the field.
Source waters tested in this study represent a wide rangeof
drinking waters typically used by populations who would
benefit from chlorine-based household water treatment
Table 7
|
Turbidity reduction using moringa powder
Source Source water turbidity (NTU) After addition of 2 grams moringa and 24 hours of settling (NTU) Percent reduction (%)
1: Rainwater 4.2 7.4 276.2
2: Lake water 28.2 3.1 89.0
3: Protected well water 40.4 2.9 92.8
4: Earth pond water 59.6 7.4 87.6
5: River water 305.0 211.0 30.8
6: Open well water 8.4 6.0 28.6
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products to improve water quality. Although further testing of
THM formation in additional water sources is warranted, this
study provides strong evidence that use of the Safe Water
System in both turbid and non-turbid waters does not cause
the formation of trihalomethanes in excess of WHO drinking
water guideline values. Thus, it is recommended that, when
microbiologic water quality cannot be assured; households
adopt or continue to use the Safe Water System or PuR
Y
in
both turbid and non-turbid waters in western Kenya.
CONCLUSIONS
Diarrheal diseases kill an estimated 2.2 million people each
year, and point-of-use chlorination options, including both
the Safe Water System and PuR
Y
, are proven interventions
that can reduce diarrheal disease incidence and protect
health in developing countries. Because the SWS includes
the addition of sodium hypochlorite to unfiltered water
sources, concerns have been raised about the potential
long-term health effects of disinfection by-products to SWS
users. The data presented herein clearly show that chlori-
nation of turbid and non-turbid waters does not lead to
trihalomethane concentrations that exceed the WHO
guideline values. Proper chlorination of household water
with the Safe Water System does not form harmful levels of
disinfection by-products. This approach to water quality
improvement and disease prevention merits wider
promotion and use.
ACKNOWLEDGEMENTS
The authors thank Philip Makutsa, Sam Ombeki, Alex
Mwaki, John Migele, Charles Komolleh, Charles Ndinya,
Mary Ayalo, and Meshak Ajode of CARE/Kenya in Homa
Bay, and Bill Gallo, Sr. for their assistance in sample
collection and logistical coordination.
DISCLAIMER
The findings and conclusions in this report are those of the
authors and do not necessarily represent the views of the
Centers for Disease Control and Prevention.
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